Hi,
The other day it crossed my mind that it could be a good way to cut the cost of your speaker cables to use higher quality cable for the red and lower quality cable for the black (ground). If the signal is going back to ground you donít need to be worried about distortion or noise I guess. Is there some people with deeper knowledge that can elaborate?

Well, speakers use an AC waveform. Current does not travel in one direction only. In either case, you should have the same type and gague wire on positive and negative since they will be carrying the same signal.
Someone correct me if I'm wrong but the negatives on an amplifier are not usually grounded.

They are at ground potential in most amplifiers, but not in balanced or bridged types,
such as BTL class D. The concern about ground is misplaced, only the potential
difference across the load matters. The wires carry the same current, and this current
flows in a loop made of the load and both wires. There is only one amplifier output current.

They are at ground potential in most amplifiers, but not in balanced or bridged types,
such as BTL class D. The concern about ground is misplaced, only the potential
difference across the load matters. The wires carry the same current, and this current
flows in a loop made of the load and both wires. There is only one amplifier output current.

Thanks for the clarification. I get that it's the potential between positive and negative. I just wasn't sure if the OP was referring the negative as earth ground or not... Probably should have said that in my first reply.

I got a Harman Kardon 330B and it’s the first time I see the black wire therminal identified as “ground”. I thought it meant earth ground. I was pretty sure I was wrong, I wanted someone to explain. Thanks again Rayma.

I think you'll find on that receiver the black speaker connectors are at chassis ground potential. However, I also think you'll find a two-wire AC line-cord vice the more contemporary three-wire cord with earth connection. So, your black speaker connections will not be at an earth potential, unless they're brought there with another piece of equipment in your system.

The only thing which matters is the total loop resistance, so you don't actually have to use the same wire for 'signal' and 'return' but there is no reason not to do this. Both are equally important, as both contribute equally to the total resistance.